World number one Serena Williams added yet another record to her glittering tennis resume by becoming the earliest qualifier for the end-of-season WTA Finals.

The Australian and French Open champion, who is bidding for a rare calendar grand slam, booked a spot at the eight-woman championship in Singapore, still more than three months away, after her Wimbledon third round win over Britain’s Heather Watson.

“I’m really thrilled to be the first player to qualify for the WTA Finals and I can’t wait to return to Singapore to defend my title,” Williams said in a WTA statement on Monday. “Last year was my first time visiting Singapore and I really enjoyed myself — the crowd is amazing and I’m excited to be going back.”

The 33-year-old American, who plays her big sister Venus in the fourth round of the grass court championships later on Monday, has won 20 grand slam singles titles and trails only Steffi Graf (22) and Margaret Court (24) in the all time list.

She had held the top spot in the rankings for 124 consecutive weeks and was the oldest woman to hold the position since the rankings were introduced in 1975, the WTA said.

The body said Williams was the fastest qualifier for their prestigious championship since the format was revamped in 2003.

WTA chairwoman and CEO Stacey Allaster was full of praise for Williams, who will be bidding for a sixth WTA Finals title on her 10th appearance when the action gets underway at Singapore’s Sports Hub from Oct. 23-Nov. 1.

“Serena is once again inspiring our fans with another historic season and I congratulate her on becoming the first player to secure her place,” Allaster said.

“I am thrilled for our fans in Singapore that they will have an opportunity to watch one of the greatest players to ever play women’s tennis.”